The invention relates to a spring-strut support bearing for supporting a motor vehicle spring strut on the body of the motor vehicle.
DE 199 35 391 A1 discloses a spring-strut support bearing, including an inner ring which has at each of its two end faces at least one elastically compliant stop buffer for limiting extreme deflecting movements in the direction of movement of the shock absorber. The stops can be provided by surface areas of the base of a flange fastened to the vehicle body or respectively, the vehicle body itself.
If a wheel, which is supported on the vehicle body via the spring strut, is moved toward the vehicle body at the moment when the spring strut undergoes a relatively large cardanic deflection from its design position, the piston rod of the shock absorber is subjected to a severe bending stress, so that it can be distorted or can even break.
The object of the invention, therefore, is to provide a spring-strut supporting bearing of the known type, with which however even with a cardanic deflection of the spring strut from the design position, compression and rebound of the guided vehicle wheel is permanently and reliably ensured.
In a motor-vehicle spring-strut support bearing for mounting a piston rod of the spring strut to a vehicle support element, the piston is mounted in the support element to a connecting element which is connected to the support element by an annular resilient spring element disposed between the connecting element and the support element and axial stops are provided including a spherically curved surface on the support element, which limit axial movement of the piston rod upon compression of the spring strut by a vehicle wheel in one direction and upon rebound of the wheel in the opposite direction, the arrangement providing a force-centering support of the spring strut piston rod on the spring strut support.
The piston rod of the shock absorber of the strut is mounted so as to be pivotable about a point located on the longitudinal axis of the piston rod. This pivot point is at the same time the central point about which the support element is spherically curved. In simplified form, the curved part of the support element may have a radius larger than its distance from the pivot point or it may even be conical. During compression or rebound of a spring strut during which the spring strut is cardanically deflected relative to the design position, a point-like engagement of a support surface, which is connected to the piston rod, with the stop can thereby be avoided. Rather, an annular supporting surface is established which centers the force transmitted by the piston rod and therefore equalizes the moments transmitted to the support element.
Since the base of the cup-like support element is not planar, but is curved or conically shaped, the rigidity of the support element is increased. This makes it possible to reduce the wall thickness of the support element and thereby saves weight.
The spring-strut bearing can have a plurality of spring or resilient elements, which, separately from one another, absorb radial or axial forces. This separation in for example first and second resilient elements is advantageous in that different elastomers having different spring and damping characteristics can be used depending on the individual tasks of the parts. However, according to the invention the spring-strut bearing can also be provided with a single-piece resilient element, which is vulcanized onto the connecting element and absorbs and transmits the radial bearing forces and the axial stop forces.
In a particular embodiment of the invention, the second spring element of the spring-strut support bearing comprises two engagement discs which, spaced apart from each other by a spacer sleeve, are clamped between the connecting element and a piston-rod shoulder. The multi-part configuration of the engagement discs ensures that the engagement discs, which are arranged one within and the other outside the support element, can be mounted. A single-piece embodiment of the connecting element, which embodiment comprises the first support disc and the spacer sleeve, is also conceivable.
In a particular refinement, the engagement discs are designed in such a manner that their sides which face the spherically curved support-element section have surface areas which are likewise spherically curved or have a conical profile. In this case, the surfaces in the design position of the spring strut, are arranged at an approximately constant distance from the surface of the support element. As a result, the elastomeric material, which, for example, is vulcanized onto the surfaces of the support discs, is less strongly deformed during contact with the supporting element, which has a life-increasing effect.
The selection of spring or resilient elements having different spring or damping characteristics enables the spring-strut support bearing to be designed so as to be capable to accommodate the stress. Thus, as a rule, softer elastomers are used for the axial stops in the bearing than for the radial support. The shaping of the resilient elements also has an effect on the damping and noise behavior of the bearing. In one refinement according to the invention therefore the damping element is bead-shaped.
Exemplary embodiments of the invention will be described in greater detail below with reference to the accompanying drawings: